Calculate floor space ratio from site and counted floor area, estimate the floor-area limit imposed by an entered allowable FSR alone, or estimate floor area and site coverage from footprint and equivalent full-area floors.

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Use locally defined counted floor and site areas. FSR arithmetic alone does not establish development permission.

Related Calculators

Floor Space Ratio Formula

The following formula is used to calculate the Floor Space Ratio (FSR):

FSR = (Total Floor Area) / (Total Land Area)

Variables:

  • FSR is the Floor Space Ratio
  • Total Floor Area is the sum of counted floor areas under the applicable local definition, across all buildings on the site (sq ft or matching area units)
  • Total Land Area is the area of the land on which the building is constructed (sq ft)

To calculate the Floor Space Ratio, divide the total floor area of the building by the total land area of the property.

What is Floor Space Ratio?

Floor Space Ratio (FSR) is counted floor area divided by site area. An allowable FSR may limit development density, but floor-area definitions, height, setbacks, site coverage and other local controls also affect what can be built. A higher FSR indicates a higher density of construction, which can impact infrastructure, traffic, and the overall character of a neighborhood.

How to Calculate Floor Space Ratio?

The following steps outline how to calculate the Floor Space Ratio (FSR).

  1. First, determine the total floor area of the building (in square feet).
  2. Next, determine the total land area of the property (in square feet).
  3. Use the formula FSR = Total Floor Area / Total Land Area.
  4. Finally, calculate the Floor Space Ratio (FSR).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Total Floor Area = 10,000 sq ft

Total Land Area = 2,500 sq ft; FSR = 10,000 ÷ 2,500 = 4:1.